The present invention relates to a process management in production and assembly lines. More particularly, the present invention pertains to a method of and apparatus for monitoring a process carried out along a line which branches and joins in a complicated manner such as that in the case where a plurality of parts or products (hereinafter referred to as "works") of various kinds are moved in a line while they are joined together, or a lot consisting of a plurality of joined works is divided into a plurality of sub-lots again.
To computerize a process monitoring operation, it is conventional practice to dispose sensors for detecting works moved in a production line and effect tracking of the works flowing in the production line in accordance with the contents of the information sent from the sensors, this tracking operation being programmed using a general-purpose computer language (see the specifications of Japanese Patent Laid-Open Nos. 35215/1981 and 129607/1983). FIG. 2 shows one example of the arrangement of a production line. A typical conventional process monitoring method will be explained below with reference to the illustrated production line.
A work (e.g., an automotive frame 1000) which is loaded on an input conveyor 30 so as to be subjected to processing is transported to an input line 36 by a carrier 32 and temporarily stored in a warehouse 38. Then, the work is transported to an input line 34 by the carrier 32, processed by process machines 37 and then transported through the input line 36 by the carrier 32 so as to be stored in the warehouse 38 again. The processed work is transported to an output conveyor 31 by the carrier 32 through an output line 35, and is then moved to a subsequent processing line by the output conveyor 31.
In such production line, the work (article) on the carrier 32 (zone 32) is tracked when moving to the input line 34 (zone 34) or the output line 35 (zone 35). A processing operation which is conducted when a load detection signal 45 for the input line 34 (zone 34) is turned ON is shown in FIG. 3. When an apparatus, (not shown) in which the above-described process monitoring transaction is computerized, detects that the load detection signal 45 is turned ON, a determination is made as to whether or not there is transaction work management data in a storage area provided in correspondence with each zone in the carrier 32 (zone 32) (Step 21). If YES, a judgement is made as to whether or not there is a space in the input line 34 (zone 34) (Step 22). If YES, a determination is made as to whether or not the destination of the top transaction in the carrier 32 (zone 32) is the input line 34 (zone 34) (Step 23). If YES, the top transaction in the zone 32 is transmitted to the zone 34 (Step 24). As will be clear from the flowchart shown in FIG. 3, the process monitoring execution program is prepared as a program for controlling the movement of the transaction in accordance with the load detection signal.
However, the conventional method, in which a program for controlling transaction is prepared and executed in accordance with the load detection signal as described above, has the following problems. Namely, the flow of transaction data is not directly expressed in the program, which means that, as the line arrangement becomes complicated, it is difficult to grasp the transaction data flow from the interrelationship between various control programs. As a consequence, when a program which has already been prepared is corrected or changed, much labor and time are needed to grasp the procedure which is to be changed.